1. Field of the Invention
The present invention relates to a carrier bearing assembly useful for reducing driveshaft vibration, noise, and stress.
2. Description of the Related Art
A universal joint (U-joint) is a type of coupling in a shaft that allows the shaft to bend while transmitting torque and rotary motion between the shaft segments. FIG. 1 illustrates the concept of operating angles of a shaft having multiple U-joints. As shown in FIG. 1, a shaft segment 1 is coupled to a shaft segment 2 using U-joint A, and the shaft segment 2 is coupled to a shaft segment 3 using U-joint B. As illustrated, each shaft segment is coupled to another at an angle, called the operating angle. For instance, the operating angle between shaft segment 1 and shaft segment 2 is a degrees (a°) and the operating angle between shaft segment 2 and shaft segment 3 is b degrees (b°). It is well known that when the operating angles a° and b° are about the same, the rotational speed of the shaft segment 1 and the shaft segment 3 will be about the same, and if the shaft segment 1 is rotated at a constant rate so too will shaft segment 3. However, where the operating angles are significantly apart, the shaft segment 3 will tend to continually accelerate/deaccelerate while the entire shaft vibrates.
On vehicles where the engine is located on a different end from the drive wheels and on many 4-wheel drive vehicles, a driveshaft is used to transfer torque from the engine/transmission to the drive wheels. To permit variations in alignment, a driveshaft typically incorporates several universal joints (U-joints).
FIG. 2 illustrates a driveshaft with non-optimal operating angles. It is to be understood that while the driveshaft shown in FIG. 2 includes two U-joints, as a practical matter, it would likely have one or more additional U-joints. It is also to be realized that for illustrative purposes the operating angles shown are exaggerated. As depicted, segment 42 is attached to segment 40 via U-joint 42u, and segment 40 is attached to segment 44 via U-joint 44u. A carrier bearing 70 is mounted to the frame of the vehicle using bolts 73, and the segment 40 of the driveshaft passes through the carrier bearing 70. However, because the operating angles are markedly apart, the driveshaft will tend to vibrate excessively. In some universal task vehicles (UTV), the driveshaft will be able to move up or down an inch or more during driving, causing extreme vibration, loud noise and stress to the driveshaft. Additionally, the bearing 70 is formed as a straight 90° hole while the driveshaft passes through the bearing 70 non-linearly. Although the carrier bearing 70 constrains movement of the driveshaft somewhat, a sizeable gap 72 exists between the driveshaft and the bearing 71 to reduce stress on the driveshaft. To remedy these problems, a rubber ring is sometimes fitted onto the bearing, but this fails to reduce noise, vibration, and constant stress to the driveshaft sufficiently.